System and method of nox abatement

ABSTRACT

A NOx abatement system comprising: a first NOx adsorber ( 18 ) capable of being disposed in-line and downstream of and in fluid communication with an engine ( 12 ); a selective catalytic reduction catalyst ( 20 ) disposed in-line and downstream of and in direct fluid communication with the first NOx adsorber ( 18 ), wherein the selective catalytic reduction catalyst ( 20 ) is capable of storing ammonia; and an off-line reformer ( 24 ) disposed in selective communication with and upstream of the first NOx adsorber ( 18 ) and the selective catalytic reduction catalyst ( 20 ), wherein the reformer ( 24 ) is capable of producing a reformate comprising primarily hydrogen and carbon monoxide.

BACKGROUND

This disclosure relates generally to a method and system for reducingnitrogen oxides (NO_(X)) and for regenerating particulate filters.

Generally, diesel engines release more undesirable NO_(X) per kilometerinto the atmosphere than gasoline engines. This is because dieselengines generally operate at higher flame temperatures in order that thediesel fuel might burn. Reduction of the flame temperatures can lead tosignificant increases in hydrocarbons, carbon monoxide, soot, and enginepower. For at least these reasons, the flame temperatures are generallynot reduced, thereby producing the NO_(X). The reduction of NO_(X) intonitrogen (N₂) by an exhaust after treatment system is increasinglydifficult as the air fuel ratio increases. The reduction of NO_(X),e.g., nitric oxide (NO), nitrogen dioxide (NO₂), and nitrous oxide(N₂O), in exhaust fluid is a widely addressed problem as a result ofenvironmental concerns and mandated government emissions regulations,particularly in the transportation industry.

One proposed solution for the reduction of NO_(X) is the use of athree-way conversion catalyst, which can be employed to treat theexhaust fluids. Such three-way conversion catalysts, containing preciousmetals such as platinum, palladium, and rhodium, can effectively useunburned hydrocarbons and carbon monoxide as reducing agents for thechemical reduction of NO_(X) in exhaust fluids, provided that the engineis operated around a balanced stoichiometry for combustion (alsoreferred to as “combustion stoichiometry”). The stoichiometric pointdepends on the fuel. For example, the balanced combustion stoichiometryfor gasoline and diesel is generally at an air to fuel ratio betweenabout 14.4 to about 14.7. However, fuel economy and global carbondioxide emission concerns have made engine operation under lean-burnconditions desirable in order to realize benefits in fuel economy. Undersuch lean-burn conditions, the air-to-fuel ratio may be greater than thebalanced combustion stoichiometry, i.e., greater than about 14.7, andmay be between about 19 to about 35. When lean-burn conditions areemployed, three-way conversion catalysts are generally efficient incompletely oxidizing the unburned hydrocarbons and carbon monoxides intocarbon dioxide and water. However, three-way conversion catalysts aregenerally inefficient in the reduction of NO_(X).

Another approach for treating NO_(X) in exhaust fluids is to incorporatea NO_(X) adsorber, also referred to as a “lean-NO_(X) trap,” in theexhaust lines. The NO_(X) adsorber promotes the catalytic oxidation ofNO_(X) by utilizing catalytic metal components effective for suchoxidation, such as precious metals. The formation of NO₂ is generallyfollowed by the formation of a nitrate when the NO₂ is adsorbed onto thecatalyst surface. The NO₂ is thus “trapped”, i.e., stored, on thecatalyst surface in the nitrate form. The system can be periodicallyoperated under fuel-rich combustion to regenerate the NO_(X) adsorber.During this period of fuel-rich combustion, the absence of oxygen andthe presence of reducing agents promote the reduction and subsequentrelease of the stored nitrogen oxides as nitrogen and water. However,this period of fuel-rich combustion may also result in a significantfuel penalty.

A more active approach, such as urea injection upon selective reductioncatalyst (SCR), can also be used for NO_(X) control. Urea selectivecatalyst reduction reduces the NO_(X) emissions in diesel engines byatomizing and dispersing aqueous urea in the flowing exhaust fluidstream. In order to effectively reduce the NO_(X) emissions, the ureaselective catalyst reduction system contains components that accuratelymeter the aqueous urea into the exhaust fluid stream and thathomogeneously disperse it in order to achieve maximum catalystutilization. These components, in addition to the urea supplyingcomponents, however, add bulk and size to the device and therebyrestrict its usage to heavy-duty applications. Further, the addedcomplexity of the urea injection and the lack of a urea distributioninfrastructure are significant detractors to using urea injection.

In addition, the urea selective catalyst reduction system is generallyoperated at elevated temperatures of greater than about 200° C., sinceurea can undergo polymerization and polymerized urea cannot bedecomposed below 200° C. In some applications, such as stop and go citydriving, the exhaust temperature does not even reach 200° C. Excesshydrocarbon must therefore be post-injected into the exhaust stream toelevate the exhaust temperature in order to decompose the polymerizedurea. The use of such elevated temperatures generally causes anundesirable amount of additional fuel to be consumed in the operation ofthe selective catalyst reduction system.

In view of the aforementioned drawbacks with the three-way conversioncatalyst, the lean-NO_(X) trap, and the urea selective catalystreduction system, it is desirable to have an onboard method and systemof a size suitable for use in light duty diesel applications e.g.,passenger cars, for purposes of reducing NO_(X) emissions as well as forregenerating particulate filters.

BRIEF SUMMARY

An embodiment of a NO_(X) abatement system comprises: a first NO_(X)adsorber capable of being disposed in-line and downstream of and influid communication with an engine; a selective catalytic reductioncatalyst disposed in-line and downstream of and in direct fluidcommunication with the first NO_(X) adsorber, wherein the selectivecatalytic reduction catalyst is capable of storing ammonia; and anoff-line reformer disposed in selective communication with and upstreamof the first NO_(X) adsorber and the selective catalytic reductioncatalyst, wherein the reformer is capable of producing a reformatecomprising primarily hydrogen and carbon monoxide.

Another embodiment of a NO_(X) abatement system comprises: an in-lineselective catalytic reduction catalyst capable of being disposed influid communication with an engine, wherein the selective catalyticreduction catalyst is capable of storing ammonia; an off-line reformerin fluid communication with the selective catalytic reduction catalyst,wherein the reformer is capable of producing a reformate comprisingprimarily hydrogen and carbon monoxide; and an off-line reactor in fluidcommunication with and downstream of the reformer, wherein the reactorcomprises an ammonia forming catalyst.

A third embodiment of a NO_(X) abatement system comprises: an off-linemembrane capable of inhibiting passage of oxygen through the membrane;an off-line reformer disposed downstream of and in fluid communicationwith the membrane and a fuel source, wherein the reformer is capable ofproducing ammonia from fuel and nitrogen; and an in-line selectivecatalytic reduction catalyst capable of being disposed downstream of andin fluid communication with an engine and the reformer, wherein theselective catalytic reduction catalyst is capable of storing ammonia.

A fourth embodiment of a NO_(X) abatement system comprises: an in-linenon-thermal plasma reactor capable of being disposed downstream of andin fluid communication with an engine; an in-line selective catalyticreduction catalyst disposed downstream of and in direct fluidcommunication with the non-thermal plasma reactor; and an off-linereformer disposed upstream of and in fluid communication with theselective catalytic reduction catalyst.

An embodiment of a method of NO_(X) abatement, comprises storing engineNO_(X) from an exhaust stream in a initial NO_(X) adsorber during astorage phase; forming reformate comprising primarily hydrogen andcarbon monoxide in an off-line reformer during a regeneration phase;reacting the reformate with the stored NO_(X) to produce ammonia duringthe regeneration phase; storing the ammonia in a selective catalyticreduction catalyst during the regeneration phase; and by-passing theexhaust stream around the initial NO_(X) adsorber during theregeneration phase.

Another embodiment of a method of NO_(X) abatement, comprises burningfuel off-line to form burner NO_(X); forming a reformate comprisingprimarily hydrogen and carbon monoxide, off-line; reacting the burnerNO_(X) with the reformate to form ammonia, off-line; storing the ammoniain an in-line selective catalytic reduction catalyst; introducing engineNO_(X) to the selective catalytic reduction catalyst; and reacting theengine NO_(X) with the ammonia.

A third embodiment of a method of NO_(X) abatement comprises passing airhaving an initial nitrogen concentration to a membrane to form amembrane effluent having a subsequent nitrogen concentration, whereinthe subsequent nitrogen concentration is greater than the initialconcentration; mixing the membrane effluent and a fuel in a mixingchamber disposed upstream of and in fluid communication with a reformer;introducing the mixed air and fuel into the reformer to produce areformate comprising ammonia; periodically introducing ammonia to aselective catalytic reductive catalyst to regenerate the catalyst;reacting the ammonia stored in the selective catalytic reductivecatalyst with NO_(X) in an exhaust fluid.

A fourth embodiment of a method of NO_(X) abatement comprisesintroducing an engine exhaust stream to a non-thermal plasma reactor;controlling a ratio of NO to NO₂ in the exhaust stream, wherein theratio is about 1:0.6 to about 1:1.5 at temperatures less than or equalto about 200° C.; forming reformate comprising primarily hydrogen andcarbon monoxide; introducing non-thermal plasma reactor effluent and thereformate to a selective reduction catalyst; and reducing the NO_(X) tonitrogen.

The above-described and other features will be appreciated andunderstood by those skilled in the art from the following detaileddescription, drawings, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Refer now to the figures, which are exemplary embodiments and whereinlike elements are numbered alike.

FIG. 1 is a partial cross-sectional view of an exemplary exhausttreatment device.

FIG. 2 is a schematic view of an embodiment of an exemplary exhausttreatment system.

FIG. 3 is a schematic view of a second embodiment of an exemplaryexhaust treatment system.

FIG. 4 is a schematic view of a third embodiment of an exemplary exhausttreatment system.

FIG. 5 is a schematic view of a fourth embodiment of an exemplaryexhaust treatment system.

FIG. 6 is a schematic view of a fifth embodiment of an exemplary exhausttreatment system.

FIG. 7 is a schematic view of a sixth embodiment of an exemplary exhausttreatment system.

FIG. 8 is a schematic view of a seventh embodiment of an exemplaryexhaust treatment system.

DETAILED DESCRIPTION

Disclosed herein is an on-board system for the production of ammoniausing on-board generated NO_(X) as well as an on-board generatedreformate comprising primarily hydrogen and carbon monoxide, i.e.,greater than or equal to 80% of the total volume of reformate ishydrogen and carbon monoxide. Preferably, greater than or equal to 90%of the reformate are hydrogen and carbon monoxide. The term “on-board”is used herein to refer to the production of a given component within avehicle (e.g., automobile, truck, etc.) system. While all embodimentsdisclosed herein use “on-board” production of ammonia and/or reformate,as will be discussed in greater detail, these components may be produced“in-line” or “off-line”. The term “line” refers to an exhaust fluidstream. As such, “in-line” refers to production of a component, e.g.,ammonia, within the exhaust fluid stream, whereas “off-line” productionrefers to the production of a given component outside of an exhaustfluid stream. The component produced “off-line” may then be introducedinto the exhaust fluid stream.

In describing the arrangement of exhaust treatment devices within asystem, the terms “upstream” and “downstream” are used. These terms havetheir ordinary meaning. For example, an “upstream” device as used hereinrefers to a device producing a fluid output stream that is fed to a“downstream” device. Moreover, the “downstream” device is the devicereceiving the output from the “upstream” device. However, it isenvisioned that a device may be both “upstream” and “downstream” of thesame device in certain configurations, e.g., a system comprising arecycle loop.

The term “direct” fluid communication is also used throughout thisdisclosure. The term “direct” as used herein refers to a communicationbetween a first point and a second point in a system that isuninterrupted by the presence of reaction devices, such as, a reactor,converter, filter, and the like, but may have other devices such asvalves, mixers, flow regulators, and the like, that are generally notused for purposes of reacting exhaust fluids or removing components froman exhaust fluid. Additionally, the term “serial” fluid communication isused herein generally to refer to fluid flow through a given device inthe order specified in that series. It is additionally noted that, wherevalves are discussed and illustrated, the valves can divert all or aportion of the flow to each conduit connected to the exiting of thevalve, i.e., the valve disposes various components in selectivecommunication (e.g., the reactor is in selective communication with theNO_(X) adsorber and the SCR because the flow from the reactor may becontrolled to be periodic).

Several combinations of exhaust treatment devices (e.g., catalyticconverters, oxidation catalysts, particulate filters, NO_(X) catalysts,NO_(X) adsorbers, plasma reactors) are discussed hereunder withreferences to individual figures. One of skill in the art will easilyrecognize that many of the devices of each of the embodiments aresimilar to or identical to each other. These various devices may beadded or omitted based on various design choices. As such, variouselements and/or features may be introduced in a given figure with theunderstanding that the systems may be modified as taught herein toinclude features illustrated in other embodiments. Each of theseelements is first introduced in the discussion of a given figure, but isnot repeated for each embodiment. Rather, distinct structure isdiscussed relative to each figure/embodiment.

Furthermore, it is noted that various exhaust treatment devices can havesimilar structural elements to each other. For example, an exhausttreatment device generally comprises a substrate, a retention materialdisposed around the substrate to form a subassembly, and a shelldisposed around the subassembly. As such, an exemplary exhaust treatmentdevice is shown in FIG. 1 to illustrate the common elements of theexhaust treatment device(s). However, distinct features of each exhausttreatment device will be discussed in greater detail when each treatmentdevice is first introduced.

Referring now to FIG. 1, an exemplary exhaust treatment device,generally designated 100, is illustrated. This exhaust treatment device100 comprises a substrate 2 located within a retention material 3forming a subassembly 4. A shell 5 is disposed around the subassembly 4.An end-cone 6, comprising a snorkel 7 having an opening 8, is inphysical communication with shell 5. Opening 8 allows exhaust fluidcommunication with substrate 2.

As will be discussed in much greater detail, various exhaust treatmentdevices can have a catalyst deposited on/throughout substrate 2(hereinafter “on”). The catalyst (as well as any support, stablizer,promoter, and the like), can be washcoated, imbibed, impregnated,physisorbed, chemisorbed, precipitated, or otherwise applied onto and/orwithin the substrate. It is further noted that catalyst metals, catalystmaterials, and the like that are introduced with respect to one exhausttreatment device may be the same with respect to another exhausttreatment device unless otherwise noted.

Substrate 2 may comprise any material designed for use in a sparkignition or diesel engine environment and having the followingcharacteristics: (1) capable of operating at temperatures up to about600° C., and up to about 1,200° C. for some applications, depending uponthe device's location within the exhaust system (manifold mounted, closecoupled, or underfloor) and the type of system (e.g., gasoline ordiesel); (2) capable of withstanding exposure to hydrocarbons, nitrogenoxides, carbon monoxide, particulate matter (e.g., soot and the like),carbon dioxide, and/or sulfur; and (3) having sufficient surface areaand structural integrity to support a catalyst.

While the materials used for the substrate may vary with the exhausttreatment device, some common materials include cordierite, siliconcarbide, metal, metal oxides (e.g., alumina, and the like), glasses, andthe like, and mixtures comprising at least one of the foregoingmaterials. These materials may be in the form of foils, perform, mat,fibrous material, monoliths (e.g., a honeycomb structure, and the like),other porous structures (e.g., porous glasses, sponges), foams, pellets,particles, molecular sieves, and the like (depending upon the particulardevice), and combinations comprising at least one of the foregoingmaterials and forms; e.g., metallic foils, open pore alumina sponges,and porous ultra-low expansion glasses.

Although the substrate 2 may have any size or geometry, the size andgeometry are preferably chosen to optimize surface area in the givenexhaust emission control device design parameters. For example, thesubstrate 2 may have a honeycomb geometry, with the combsthrough-channel having any multi-sided or rounded shape, withsubstantially square, triangular, pentagonal, hexagonal, heptagonal,octagonal, or similar geometries preferred due to ease of manufacturingand increased surface area.

Located between the substrate 2 and the shell 5 may be a retentionmaterial 3 that insulates the shell 5 from both the exhaust fluidtemperatures and the exothermic catalytic reaction occurring within thecatalyst substrate 2. The retention material 3, which enhances thestructural integrity of the substrate 2 by applying compressive radialforces about it, reducing its axial movement and retaining it in place,may be concentrically disposed around the substrate 2 to form aretention material/substrate subassembly 4.

The retention material 3, which may be in the form of a mat,particulates, or the like, may be an intumescent material (e.g., amaterial that comprises vermiculite component, i.e., a component thatexpands upon the application of heat), a non-intumescent material, or acombination thereof. These materials may comprise ceramic materials(e.g., ceramic fibers) and other materials such as organic and inorganicbinders and the like, or combinations comprising at least one of theforegoing materials. Non-intumescent materials include materials such asthose sold under the trademarks “NEXTEL” and “INTERAM 1101HT” by the“3M” Company, Minneapolis, Minn., or those sold under the trademark,“FIBERFRAX” and “CC-MAX” by the Unifrax Co., Niagara Falls, N.Y., andthe like. Intumescent materials include materials sold under thetrademark “INTERAM” by the “3M” Company, Minneapolis, Minn., as well asthose intumescents which are also sold under the aforementioned“FIBERFRAX” trademark, as well as combinations thereof and others.

The retention material/substrate subassembly 4 may be concentricallydisposed within a shell 5. The choice of material for the shell 5depends upon the type of exhaust fluid, the maximum temperature reachedby the substrate 2, the maximum temperature of the exhaust fluid stream,and the like. Suitable materials for the shell 5 may comprise anymaterial that is capable of resisting under-car salt, temperature, andcorrosion. For example, ferrous materials may be employed such asferritic stainless steels. Ferritic stainless steels may includestainless steels such as, e.g., the 400—Series such as SS-409, SS-439,and SS-441, with grade SS-409 generally preferred.

End cone 6 (or alternatively an end cone(s), end plate(s), exhaustmanifold cover(s), and the like), which may comprise similar materialsas the shell, may be disposed at one or both ends of the shell. The endcone 6 is sealed to the shell to prevent leakage at the interfacethereof. These components may be formed separately (e.g., molded or thelike), or may be formed integrally with the housing using methods suchas, e.g., a spin forming, or the like.

Referring now to FIG. 2, an exhaust treatment system generallydesignated 200 is illustrated. While the location, number, and size, ofeach component may vary, this figure provides a starting point fordiscussion. The exhaust treatment system 200 comprises an engine 12.While the engine may be a gasoline engine or a diesel engine, thesystem(s) illustrated herein are preferably for diesel engine systems.Disposed in fluid communication with engine 12 is a first oxidationcatalyst 14, a particulate filter 16, a NO_(X) adsorber 18, and aSelective Catalytic Reduction (SCR) catalyst 20. An arrow labeled“exhaust flow direction” indicates the general flow of the exhaust in anexhaust conduit 22. The exhaust conduit 22 is in fluid communicationwith each component in the system. For example, in an exemplaryembodiment, the general directional flow of exhaust fluid from theengine 12 may be through first oxidation catalyst 14, particulate filter16, NO_(X) adsorber 18, and SCR catalyst 20. After passing through SCRcatalyst 20, the exhaust fluid may then be discharged into an externalenvironment.

In various embodiments, system 200 devices may be added or removed. Forexample, particulate filter 16 may be omitted in various embodiments. Inother embodiments, NO_(X) adsorber 18 may also be omitted. Conversely,for example, additional exhaust treatment device(s) (e.g., NO_(X)adsorber(s), SCR catalyst(s), and/or the like) may be added to thesystem. The additional NO_(X) adsorber(s) and/or SCR catalyst(s) arepreferably arranged in parallel. The advantages of arranging varioussystem devices in parallel will be discussed in greater detail below.

Oxidation catalyst 14 comprises a catalytic metal, support material(s),and a substrate. The catalytic metal(s) may be disposed on the supportmaterial, which is disposed on the substrate. Examples of catalyticmetals include, but are not limited to, platinum, palladium, ruthenium,rhodium, iridium, gold, and silver, as well as oxides, alloys, salts,and mixtures comprising at least one of the foregoing metals.

The catalytic metal can comprise, for example, up to about 95 wt %platinum (e.g., about 60 wt % to about 95 wt %) and up to about 50 wt %palladium and/or rhodium (e.g., about 10 wt % to about 50 wt %), basedon the total weight of catalytic metal(s). Within this range, greaterthan or equal to about 60 wt % of platinum is preferred. Also withinthis range, less than or equal to about 95 wt % of platinum ispreferred, with less than or equal to about 70 wt % more preferred.Within the foregoing range, greater than or equal to about 10 wt % ofpalladium or rhodium is preferred, with greater than or equal to about20 wt % more preferred. Also within this range, less than or equal toabout 40 wt % is preferred, with less than or equal to about 30 wt %more preferred.

Preferably, oxidation catalyst 14 comprises support materials. Suchmaterials include, but are not limited to, gamma aluminum oxide, deltaaluminum oxide, theta aluminum oxide, stabilized aluminum oxides,titanium oxides, zirconium oxides, yttrium oxides, lanthanum oxides,cerium oxides, scandium oxides, and the like, as well as combinationscomprising at least one of the foregoing. Particularly a mixture oflanthanum stabilized (gamma or delta phase) aluminum oxide, atitanium-zirconium solid solution, or a combination comprising at leastone of these support materials is preferred.

The support material(s) can be employed at about 0.5 grams per cubicinch (g/in³) (about 0.03 grams per cubic centimeter (g/cm³)) to about6.0 g/in³ (about 0.4 g/cm³), based on the volume of the substrate.Within this range, greater than or equal to about 1.0 g/in³ (about 0.06g/cm³) is preferred, more preferably greater than or equal to about 2.0g/in³ (about 0.1 g/cm³), and most preferably greater than or equal toabout 3.0 g/in³ (about 0.2 g/cm³). Also within this range, less than orequal to about 6.0 g/in³ (about 0.4 g/cm³) is preferred, more preferablyless than or equal to about 5.0 g/in³ (about 0.3 g/cm³), and mostpreferably less than or equal to about 4.0 g/in³ (about 0.2 g/cm³). Thecatalytic metal loadings can comprise about 0.005 wt % to about 25.0 wt%, wherein the weight percent is based on the total weight of thesupport material(s) and catalytic metal(s).

Preferably, the substrate includes, but is not limited to, cordierite,mullite, alpha-aluminum oxide, aluminum phosphate, aluminum titanate,aluminosilicate, zirconium oxide, titanium oxide, titanium phosphateand/or magnesium silicate. Preferably, the substrate has an extrudedhoneycomb cell geometry comprising greater than or equal about 400 cellsper square inch, and a wall thickness of less than or equal to about 8.0mils (about 0.02 cm).

In an exemplary embodiment, the support material comprises two parts,labeled Part 1 component and Part 2 component merely for clarity in thefollowing discussion. Part 1 component as used herein refers to asupport material having an agglomeration of primary particles, whereinthe agglomeration size (taken along the major diameter (i.e., thelongest diameter)) is about 5 micrometers to about 15 micrometers andthe primary particle size is less than or equal to about 300 nanometers.The term “agglomerate” is used herein to refer to a cluster or group ofprimary particles. The term “primary particle” is used herein togenerally refer to the individual constituent particles forming theagglomerate. In other words, a primary particle is a single particle,whereas an agglomerate comprises at least two primary particles. Part 2component as used herein refers to a support material having a primaryparticle size of less than or equal to about 500 nanometers, whereinPart 2 components preferably have an agglomerate size of less than orequal to about 0.5 micrometers, with less than or equal to about 0.3micrometers preferred, and less than or equal to about 0.2 micrometersmore preferred.

Preferably, Part 1 component and Part 2 component are mixed together andapplied to the substrate to form a support material layer having athickness of less than or equal to about 120 micrometers, with athickness of about 80 micrometers to about 100 micrometers preferred.Preferably, a ratio of Part 1 component to Part 2 component is about80:20 to about 20:80. In an exemplary embodiment, the catalytic metalmay be disposed on Part 1 component and on Part 2 component,individually, before mixing the components.

Part 1 component can comprise an alkaline earth, an alkaline metal, or arare earth stabilized aluminum oxide. Preferably, the stabilizedaluminum oxide is stabilized gamma aluminum comprising a sufficientamount of stabilizer to prevent the alumina from transforming to alphaalumina with a temperature exotherm of less than or equal to about 800°C.; e.g., up to about 20 wt % stabilizer, with about 0.5 wt % to about15 wt % preferred, and about 2 wt % to about 6 wt % more preferred,wherein weight percents are based on the total weight of the stabilizedaluminum oxide. The Part 2 component can comprise an alkaline earth, analkaline metal or a rare earth stabilized solid solution. Preferably,the stabilized solid solution comprises up to about 20 wt % stabilizer,with about 0.5 wt % to about 15 wt % preferred, and about 6 wt % toabout 12 wt % especially preferred. All ranges disclosed herein areinclusive and combinable (e.g., ranges of up to about 25 wt %, withabout 5 wt % to about 20 wt % desired, and about 10 wt % to about 15 wt% more desired, would therefore include the ranges of about 5 wt % toabout 25 wt %, about 10 wt % to about 25 wt %, about 5 wt % to about 15wt %, etc.).

The rare earth(s) comprising Part 1 and/or Part 2 may be selected fromscandium, yttrium, lanthanum, cerium, praseodymium, neodymium,dysprosium, and ytterbium.

The alkaline earths, alkaline earth metals and rare earths may beintroduced, for example, as particulate oxides, carbonates,oxychlorides, sulfates, soluble inorganic solutions (e.g., of nitrates,chlorides, fluorides, bromides, sulfides, ammines, and/or hydroxides),soluble organic solutions (e.g., of carboxylates, acetates, citrates,and/or formats), or colloidal sols e.g., of ethoxides, methoxidesmethoxyethanols, isopropoxides, and/or the like), and the like, as wellas combinations comprising at least one of the foregoing.

Part 1 materials include, but are not limited to barium stabilizedgamma, delta and/or theta aluminum oxide, lanthanum stabilized gamma,delta and/or theta aluminum oxide, barium-aluminate, bariumhexaaluminate, and the like, as well as combinations comprising at leastone of the foregoing, with lanthanum stabilized gamma-delta aluminumoxide desirable.

Part 2 materials include solid solutions including, but not limited to,titanium-zirconium oxide, yttrium-zirconium oxide, barium-zirconiumoxide, lanthanum-titanium oxide and the like, as well as combinationscomprising at least one of the foregoing, withlanthanum-titanium-zirconium oxide desirable. Advantageously, solidsolutions can impede grain growth of the catalyst metal in stronglyreducing environments (e.g., an environment comprising an air to fuelratio of less than or equal to 11), thereby, improving the catalystendurance.

The particulate filter 16 can comprise any filter and design capable ofremoving particulate matter from the exhaust stream and preventing theemission of such particulate matter into the atmosphere. Preferably, theparticulate filter comprises a gas permeable ceramic material having ahoneycomb structure comprising a plurality of channels, preferablyparallel channels. The channels can be divided into alternating inletchannels and exit channels. The inlet channels are open at an inlet endof the filter element and are preferably plugged at the exit end of thefilter. Conversely, exit channels are preferably plugged at the inletend and open at the exit end of the filter. The inlet and exit channelsare separated by porous sidewalls, that permit the exhaust gases to passfrom the inlet channels to the exit channels along their length.

The particulate filter 16 generally comprises a shell, a retentionmaterial, and a filter element (e.g., substrate). Materials for theshell and the retention material may include those listed above withregard to an exemplary exhaust treatment device.

The filter element is generally desired to filter out the particulatematter present in the exhaust. It may generally be manufactured frommaterials such as ceramics such as cordierite, metallics such assintered stainless steel powder, carbides (such as silicon carbide),nitrides (such as silicon nitride), and the like, as well ascombinations comprising at least one of the foregoing materials. Suchmaterials preferably possess a sufficient porosity to permit the passageof exhaust gas and reformate through the element walls, and yet filterout a substantial portion, if not all of the particulate matter presentin the exhaust. Preferably the filter has greater than or equal to about20% porosity and more preferably greater than or equal to about 40%porosity. Preferably, the filter pores through the substrate have amajor diameter of less than or equal to about 30 micrometers and morepreferably less than or equal to about 20 micrometers. Preferably thefilter pores are greater than or equal to about 0.1 micrometer and morepreferably greater than or equal to about 0.4 micrometers.

The particulate filter element may optionally include a catalyst on thefilter element (e.g., a coating of a catalyst material). Preferably, thecatalyst material performs a reforming function, e.g., a water gas shiftcatalyst (WGS) that converts carbon monoxide and water into hydrogen andcarbon dioxide. Examples of WGS catalyst metals include, but are notlimited to, platinum, palladium, rhodium, ruthenium, their oxides, andthe like as well as combinations comprising at least one of theforegoing metals and/or their oxides. The WGS catalyst may be disposedon support material(s). Suitable support materials include thosediscussed above with respect to oxidation catalyst 14. Preferably, thesupport materials include aluminum oxide, silicon oxide, zirconiumoxide, titanium oxide, and the like, as well as combinations comprisingat least one of the following. Preferably, the WGS catalyst comprises aplatinum impregnated lanthanum-titanium-yttrium-zirconium solidsolution.

Additionally, the catalyst material may include a promoter oxide(s) suchas vanadium, chromium, manganese, iron, cobalt, copper, lanthanum,cerium, praseodymium, neodymium, ytterbium, or a mixture comprising oneor more of the foregoing promoter oxides.

The catalyst material can be at a loading sufficient to convert greaterthan or equal to about 50% (vol %) of the water present in the exhaustto hydrogen; e.g., about 0.05 g/in³ (about 0.003 g/cm³) to about 4.0g/in³ (about 0.2 g/cm³), with about 0.2 (about 0.01 g/cm³) to about 1.0g/in³ (about 0.06 g/cm³) preferred. The WGS catalyst metal(s) portioncan be present in an amount of about 0.01 g/in³ (about 0.0006 g/cm³) toabout 0.11 g/in³ (about 0.007 g/cm³) of substrate with about 0.02 g/in³(about 0.001 g/cm³) to about 0.04 g/in³ (about 0.002 g/cm³) preferred.The promoter oxide(s) can be present in an amount of about 0.1 g/in³(about 0.006 g/cm³) to about 1.2 g/in³ (about 0.07 g/cm³), with about0.4 g/in³ (about 0.02 g/cm³) to about 0.7 g/in³ (about 0.04 g/cm³)preferred. The support materials portion can be present in an amount ofabout 0.7 g/in³ (about 0.04 g/cm³) to about 1.9 g/in³ (about 0.1 g/cm³)with about 1.2 g/in³ (about 0.07 g/cm³) to about 1.6 g/in³ preferred.The promoter oxide and support oxide average particle diameters arepreferably less than or about 2 micrometers and preferably less than orequal to about 10 micrometers, with less than or about 90 percent of theparticles having an average particle diameter of about 3 micrometers toabout 6 micrometers preferred e.g., an average particle diameter of 4.4micrometers.

The NO_(X) adsorber 18 generally comprises a substrate, catalyticmetal(s), support materials, and NO_(X) trapping material(s). Thecatalytic metal component, the catalytic metal support, and the NO_(X)trapping materials can be washcoated, imbibed, impregnated, physisorbed,chemisorbed, precipitated, or otherwise applied onto and/or within theporous substrate.

Additionally, the substrate may comprise a protective coating that isapplied to the substrate before the substrate receives the catalyst(e.g., is washcoated). Preferably, the protective coating comprises ametal phosphate. The metal phosphate reduces fluxing of the substratedue in particular to migration of the NO_(X) trapping materials such asbarium and potassium.

For example, zirconium phosphate can bond with the zirconia that ispresent in a cordierite substrate improving the strength of thin wallsubstrate, e.g., 900 cells/in² with 2 mil (about 0.005 cm) walls.Zirconium phosphate is preferably applied to cordierite substrate usinga dipping process, and then calcined to at least 400° C. The resultingcoating of zirconium phosphate has a thickness of greater than to about10 nanometers, with greater than to about 8 nanometers preferred, andgreater than to about 4 nanometers more preferred. Zirconium phosphateis resistant to both basic and acidic conditions, to corrosive materialssuch as nitrates, chlorides, hydroxides, alkaline earth oxides, alkalinemetal oxides, transition metal oxides, rare earth oxides, precious metalsalts, reducing gasses such as hydrogen and carbon monoxide, as well asacidic gasses such as nitrogen oxides and sulfur oxides.

The substrate may include those designs and material as described abovewith respect to the exemplary exhaust treatment device. For example,some possible substrate materials include cordierite, mullite, metallicfoils, zirconium toughened aluminum oxide, silicon carbide and the like,and mixtures comprising at least one of the foregoing materials.Preferably, the NO_(X) adsorber substrate is a cordierite substrate withan extruded honeycomb cell geometry comprising less than or about 600cells per square inch, and a wall thickness of less than or equal toabout 4.0 mils (about 0.01 cm).

The catalytic metal of NO_(X) adsorber 18 comprises those listed abovewith respect to oxidation catalyst 14. The catalytic metal is present inan amount sufficient to partially reduce NO_(X) to NH₃; e.g., an amountof about 0.01 wt % to about 4.0 wt %, based on the total weight of thecatalytic metal, catalytic metal support material, and NO_(X) trappingmaterial, about 0.5 wt % to about 2.0 wt % preferred.

Where the catalytic metal is a combination of rhodium with one or moreother metals, the other metals, e.g., palladium, platinum, and the like,are present in an amount less than the rhodium. For example, with aplatinum/rhodium combination, the catalytic metal comprises about 70 wt% to about 95 wt % rhodium and about 5 wt % to about 30 wt % platinum.Within this range, for a platinum/rhodium combination it is generallydesirable to have an amount of rhodium of greater than or equal to about75 wt %, and preferably greater than or equal to about 85 wt %, based onthe total weight of the combination. Within this range, it is alsodesirable to use the platinum in an amount of less than or equal toabout 20 wt %, and preferably in an amount of less than or equal toabout 10 wt %, based on the total weight of the combination.

The support material of NO_(X) adsorber 18 can comprise supportmaterials to those previously listed above with respect to oxidationcatalyst 14. For example, the support materials include, but are notlimited to, zirconium oxides, zinc oxide, gamma aluminum oxide, deltaaluminum oxide, theta aluminum oxide, stabilized aluminum oxides,alkaline earth aluminates transition metal hexaaluminates and the like,as well as combinations comprising at least one of the foregoing, andmore particularly zinc-zirconium solid solutions.

In addition to the catalytic metal, the support materials may be furtherloaded NO_(X) trapping material(s), such as alkali metal oxides,alkaline earth metal oxides, and mixtures comprising at least one of theforegoing metal oxides. Suitable trapping materials include oxides ofbarium, strontium, calcium, magnesium, cesium, lithium, sodium,potassium, magnesium, rubidium and the like, and combinations comprisingat least one of the foregoing, and more particularly a mixture of oxidesof barium and potassium.

The NO_(X) trapping material can be employed at an amount sufficient toadsorb NO_(X;\) e.g., at greater than to about 28 wt %, based on thecombined total weight of the catalytic metal, support materials, NO_(X)trapping material, and hydrophobic material (“NO_(X) combined weight”),with about 4 wt % to about 28 wt % preferred, about 8 wt % to about 22wt % more preferred, and about 12 wt % to about 16 wt % even morepreferred. The catalytic metal can be employed at about 0.1 wt % toabout 4.0 wt % based on the NO_(X) combined weight. Within this range,greater than or equal to about 0.5 wt % is preferred, greater than orequal to about 0.75 wt % is more preferred, and greater than or equal toabout 1.0 wt % is most preferred. Also within this range, less than orequal to about 4.0 wt % is preferred, less than or equal to about 3.0 wt% is more preferred, and less than or equal to about 2.0 wt % is mostpreferred.

Further, the NO_(X) trapping material may be coated with a hydrophobicmaterial such as titanium oxide. Suitable titanium sources generallyinclude titanium oxychloride, titanium oxynitrate, titanium isobutoxide,titanium n-butoxide, titanium tert-butoxide, titanium ethoxide, titaniumisopropoxide, titanium methoxide, titanium n-propoxide and colloidaltitanium oxide. Preferably, the hydrophobic material is present in anamount sufficient to render the NO_(X) trapping material hydrophobic,e.g., about 0.1 wt % to about 2 wt %, with 0.2 wt % to about 1 wt % morepreferred, wherein the weight percentages are based on the NO_(X)combined weight.

The SCR catalyst 20 generally comprises a substrate, catalytic metal(s),support materials, and ammonia (NH₃) trapping material(s). Suitable NH₃trapping materials include vanadium oxides, niobium oxides, molybdenumoxides, tungsten oxides, rhenium oxides, and the like, and combinationscomprising at least one of the foregoing. Generally, the substrate, thecatalytic metal(s), and the support materials employed in the SCRcatalyst 20 are substantially the same as that used in NO_(X) adsorber18. Preferably, the catalytic metal can be employed at about 0.01 wt %to about 4.0 wt %, based on the total weight of the catalytic metal,catalytic metal support, and NH₃ trapping component. Within this range,greater than or equal to about 0.01 wt % is preferred, more preferablygreater than or equal to about 0.1 wt %, and most preferably greaterthan or equal to about 0.2 wt %. Also within this range, less than orequal to about 4.0 wt % is preferred, more preferably less than or equalto about 3.0 wt %, and most preferably less than or equal to about 2.0wt %.

Where the catalytic metal is a combination of rhodium with one or moreother metals, the other metals, e.g., palladium, platinum, and the like,are present in an amount less than the rhodium. For example, with aplatinum/rhodium combination, the catalytic metal component can compriseabout 70 wt % to about 95 wt % rhodium and about 5 wt % to about 30 wt %platinum. Within this range, for a platinum/rhodium combination it isgenerally desirable to have an amount of greater than or equal to about75 wt %, and preferably greater than or equal to about 85 wt % rhodiumbased on the total weight of the combination. Within this range, it isalso desirable to use the platinum in an amount of less than or equal toabout 20 wt %, and preferably in an amount of less than or equal toabout 10 wt % based on the total weight of the combination.

The NH₃ trapping material(s) component can be employed in an amountsufficient to trap breakthrough NH₃. Generally it will be employed inamount about 32 wt %, based on the total weight of the catalytic metalcomponent(s), support materials and NH₃ trapping materials (“SCRcombined weight”). Within this range, greater than or equal to about 2wt % is preferred, greater than or equal to about 4 wt % more preferred,and greater than or equal to about 6 wt % even more preferred. Alsowithin this range, less than or equal to about 18 wt % is preferred,less than or equal to about 14 wt % more preferred, and less than orequal to about 10 wt % even more preferred. The catalytic metalcomponent can be employed at about 0.01 wt % to about 4.0 wt %, based onthe SCR combined weight. Within this range, greater than or equal toabout 0.01 wt % is preferred, greater than or equal to about 0.5 wt %more preferred, and greater than or equal to about 1.0 wt % even morepreferred. Also within this range, less than or equal to about 6.0 wt %is preferred, less than or equal to about 4.0 wt % more preferred, andless than or equal to about 2.0 wt % even more preferred.

Preferably, SCR substrate is a cordierite substrate with an extrudedhoneycomb cell geometry comprising less than 900 cells per square inch,and a wall thickness of less than or equal to 4.0 mils (about 0.01 cm).In addition to the catalytic metal(s), the support materials, and theNH₃ trapping materials, the substrate may comprise a protective coatingof phosphate (e.g., metal phosphate) preferably disposed between thesubstrate and the NH₃ tapping materials. The phosphate reduces fluxingof the porous support due to the NH₃ trapping materials, such asvanadium oxides, niobium oxides, molybdenum oxides, tungsten oxides,and/or, rhenium oxides,

Referring now to FIG. 3, an exemplary exhaust treatment system generallydesignated 300 is illustrated. A fuel source 26 is in direct fluidcommunication with a reformer 24. Reformer 24 is capable of direct fluidcommunication with oxidation catalyst 14, particulate filter 16, and/orNO_(X) adsorber 18. Reformate (e.g., hydrogen, carbon monoxide,partially oxidized organics such as aldehydes, ketones and carboxylicacids, and/or light gasses such as methane, ethane, propane, and/orbutane) from reformer 24 may be selectively directed to oxidationcatalyst 14, particulate filter 16, and/or NO_(X) adsorber 18 via valve28. Preferably, the reformate comprises primarily hydrogen and carbonmonoxide, i.e., greater than or equal to 80% of the total volume ofreformate is hydrogen and carbon monoxide, with greater than or equal to90% preferred. The reformate may be used to regenerate oxidationcatalyst 14, particulate filter 16, and/or NO_(X) adsorber 18. Adiscussion of using reformate to selectively regenerate an oxidationcatalyst(s), particulate filter(s), and/or NO_(X) adsorber(s) is foundin U.S. patent application Ser. No. 10/301,455, which is hereinincorporated by reference.

For example, high temperature hydrogen gas, e.g., reformate at about600° C., and thermal energy generated from partial oxidation reactionsin the reformer 24 can be used to regenerate the particulate filter 16.For example, hydrogen (e.g., reformate) can be introduced upstream ofoxidation catalyst 14 (disposed upstream of and in direct fluidcommunication with particulate filter 16) to generate an exotherm. Theexotherm preferably raises the exhaust temperature to a temperature ofgreater than or equal to about 300° C., and with greater than or equalto about 350° C. more preferred. However, it is noted that the reformateexiting the reformer may be at a temperature greater than or equal toabout 300° C., thereby aiding in elevating the temperature of theexhaust fluid when the reformate is disposed in the exhaust conduit 22.In various embodiments, the conduit 22 may be designed to minimize theheat transferred to the atmosphere, e.g., conduit 22 may be doublewalled. The heat generated can initiate combustion of trappedparticulates in the particulate filter 16. In various other embodiments,particulate filter 16 may further comprise a catalyst, as describedabove. As such, reformate comprising hydrogen and carbon monoxide may bedisposed direct fluid communication with the particulate filter 16(e.g., reformate can be introduced to exhaust conduit 22, upstream ofparticulate filter 16 and downstream of oxidation catalyst 14) togenerate the exotherm.

The reformate in system 300 can also be employed for the production ofammonia that can be adsorbed by the SCR catalyst 20. As will bedescribed in greater detail below, NO₂ trapped in the NO_(X) adsorber 18reacts with hydrogen in an oxygen depleted environment to produceammonia. Since the NO_(X) adsorber 18 does not have an affinity forstrong bases like ammonia, the ammonia does not remain upon the NO_(X)adsorber 18. Rather, the ammonia flows downstream to SCR catalyst 20.Accordingly, SCR catalyst 20 is preferably located downstream and indirect fluid communication with NO_(X) adsorber 18. The ammonia adsorbedon the SCR catalyst 20 may be used to reduce an equal amount of NO_(X)present in the exhaust fluid stream. As such, the NO_(X) adsorber 18 isthus regenerated by the conversion of the trapped NO_(X) into NH₃ andthe SCR catalyst is regenerated by the chemical reaction between NO_(X)and NH₃ forming the reaction products nitrogen and water.

Valve 30 controls the exhaust fluid flow entering NO_(X) adsorber 18.Valve 30 may be used to divert exhaust fluid flow to the NO_(X) adsorber18 during a NO_(X) storage phase. During this NO_(X) storage phase,exhaust fluid from the engine 12 is directed to the NO_(X) adsorber 18where NO_(X) present in the exhaust fluid is trapped/adsorbed onto theNO_(X) adsorber 18. For example, a NO_(X) trapping phase may comprise aduration of about 60 seconds. Reformer 24 can be inactive and valve 30closed during the NO_(X) trapping phase. A reduction/regeneration phasemay then comprise a duration of about 4 seconds where the reformer 24 isactive (directing reformate to NO_(X) adsorber 18) and valve 30 is opensuch that NO_(X) travels to the SCR where it reacts with stored NH₃.

Additional valves may be added to the system(s) to further regulate flowfrom the reformer 24, engine 12, and/or any other component in thesystem. As such, it is understood that any discussion of any given valvemay also be applied to any other valve in the system. For example,valves 28 and 30 may comprise a spool, butterfly, ball valve, or similarconfigurations capable of selectively allowing and inhibiting flow.Preferably, valve 30 is a two-way poppet valve. The valve(s) may be ininformation/command (e.g., electrical) communication with a controller(not shown). The controller may be programmed, for example, such thatthe NO_(X) adsorber 18 can be regenerated as needed. For example, insystem 300, the controller may be programmed to divert the exhaust fluidby manipulating valve 30 based upon NO_(X) slip (i.e., the NO_(X)remaining in the exhaust fluid after exiting a system component, e.g.,NO_(X) adsorber 18), engine schedule, time, and/or a combination of theforegoing. Valves 28 and 30 can also be programmed to provideintermittent flow, for example, a pulse, of hydrogen and carbon monoxideinto particulate trap 16, oxidation catalyst 14, and/or NO_(X) adsorber18.

As briefly mentioned above, the NO_(X) adsorber 18 promotes thecatalytic oxidation of NO_(X) by catalytic metal effective for suchoxidation. The formation of NO₂ is generally followed by the formationof a nitrate when the NO₂ is adsorbed onto the catalyst surface. The NO₂is thus “trapped” (i.e., stored) by the NO_(X) trapping materials on thecatalyst surface in the nitrate form. This mode of operation is referredto as the storage phase of the NO_(X) adsorber 18. In this storage phaseof operation, the air to fuel ratio is greater than 14.7. In this sameoperating condition, the air to fuel ratio is typically less than about50.

During a regeneration phase of the NO_(X) adsorber 18, the valve 30 iscycled to divert the exhaust fluid through a by-pass conduit 34, whichdiverts the exhaust flow around NO_(X) adsorber 18. At the same time,reformate (i.e., reducing agents) is then introduced into reformateconduit 32, which is in fluid communication with NO_(X) adsorber 18. Asthe carbon monoxide reductant consumes oxygen, the air to fuel ratiodecreases to less than or equal to about 12 (e.g., about 8.0 to about12.4), and the reductant hydrogen reacts with NO_(X) in the NO_(X)adsorber 18 producing the reductant NH₃. The reductant NH₃ then collectsin SCR catalyst 20 located downstream from NO_(X) adsorber 18. Forexample, the SCR catalyst 20 may store the reducing agent as ammonia orreact with water forming ammonium hydroxide. Since both flow pathways(i.e., a first fluid pathway is defined as flow through NO_(X) adsorber18 and a second fluid pathway is defined as flow around the NO_(X)adsorber 18 through by-pass conduit 34) merge at SCR catalyst 20, theexhaust fluid that had been diverted around NO_(X) adsorber 18 viaby-pass conduit 34 may be used to react as strong acid (e.g., NO_(X) andHNO₃) with the strong base (e.g., NH₃ and NH₄OH) on the SCR catalystsurface, forming nitrogen and water. After completion of thisregeneration cycle, valve 30 is cycled back such that the flow ofexhaust fluid is again through the first exhaust pathway, i.e., throughNO_(X) adsorber 18.

The above-described reactions between carbon monoxide and oxygen,hydrogen and NO_(X) occur at temperatures of about 140° C. to about 400°C. Within this range, it is generally desirable to conduct the reactionat a temperature of greater than or equal to about 180° C., preferablygreater than or equal to about 220° C., and more preferably greater thanor equal to about 240° C. Also desirable within this range, is atemperature of less than or equal to about 400° C., preferably less thanor equal to about 320° C., and more preferably less than or equal toabout 280° C. Reaction of the hydrogen and carbon monoxide with theNO_(X) adsorber 18 creates an exotherm, which may drive some non-reducedNO_(X) or partially reduced NO_(X) (e.g., N₂O) from NO_(X) adsorber.These non-reduced and partially reduced species are, however, fullyreduced when they reach the SCR catalyst 20.

It is noted that NO_(X) adsorber 18 has little chemical affinity forstrong bases such as ammonia and hydrogen sulfide. Therefore, asdescribed above, the ammonia generated from the NO_(X) in the NO_(X)adsorber 18 is released from the acid adsorbing NO_(X) adsorber 18, andcollects downstream in the base adsorbing SCR catalyst 20, where it isused to reduce the acidic NO_(X) that may be present in the exhaustfluid being introduced into the SCR catalyst 20 from by-pass conduit 34.In various embodiments, the NO_(X) adsorber 18 and the SCR catalyst 20can be disposed in the same housing. Actually, it is envisioned thatmany of the various substrates (filters, catalyzed substrates, and thelike), can be disposed in the same housing in the relationshipsdescribed herein (e.g., upstream/downstream of the other substrates,etc., accordingly, with spaces between the substrates where desired toenable reformate introduction).

Examples of the fuel source 26 include hydrocarbon fuels such asgasoline, diesel, ethanol, methanol, kerosene, and the like; gaseousfuels, such as natural fluid, propane, butane, and the like; andalternative fuels, such as hydrogen, biofuels, dimethyl ether, and thelike; as well as combinations comprising at least one of the foregoingfuels. The selection of fuel source 26 is based upon application,expense, availability, and environmental issues relating to the fuelsource 26. The preferred fuel source is diesel since it is readilyavailable on the vehicle. Examples of diesel fuels that can be processedin the reformer 16 include commercial diesel fuels, military dieselfuels, blended diesel fuels containing a larger than normal “light end”component (for example diesel blended with naphtha, kerosene, and/ormethanol), and the like, as well as combinations comprising at least oneof the foregoing diesel fuels.

Reformer 24 generally generates reformate comprising hydrogen, carbonmonoxide, and other byproducts that may include carbon dioxide, and insome cases hydrogen sulfide. Reformer 24 may be configured for partialoxidation, steam reforming, or dry reforming. Preferably, reformer 24 isconfigured primarily for partial oxidation reforming. However, it isnoted that steam reforming and dry reforming may also occur to theextent of the water and carbon dioxide contained in the air and fuel.

Partial oxidation reformers are based on sub-stoichiometric combustionto achieve the temperatures sufficient to reform the hydrocarbon fuel.This reaction is exothermic, which causes the reformate to emerge fromthe reformer 24 at temperatures of about 700° C. to about 1,000° C.Catalysts can be used with partial oxidation systems (catalytic partialoxidation) to promote conversion of various fuels, such as ethanol, intoa synthetic fluid. The use of the catalyst can result in an accelerationof the reforming reactions and can provide this effect at lower reactiontemperatures than those that would otherwise be required in the absenceof a catalyst. An example of the partial oxidation reforming reaction isas follows:CH₄+½O₂→CO+2H₂+heat  (I)

In contrast to partial oxidation reformers, steam configured reformersreact fuel and steam in heated tubes filled with catalysts to converthydrocarbons in the fuel into primarily hydrogen and carbon monoxide. Anexample of the steam reforming reaction is as follows:CH₄+H₂O→CO+4H₂  (II)

Dry reforming systems form hydrogen and carbon monoxide in the absenceof water, for example, by using carbon dioxide. An example of the dryreforming reaction is depicted in the following reaction:CH₄+CO₂→2CO+2H₂  (III)

Reformer 24 preferably comprises a porous substrate, a catalytic metalcomponent and a support material. Preferably, the catalytic metalcomponent is a combination of rhodium with other metals. The othermetals, e.g., platinum, and the like, can be present in an amount lessthan the rhodium. In the case of a platinum-rhodium combination, thecatalytic metal component can comprise up to about 95 wt % rhodium andup to about 30 wt % platinum, based on the total weight of the catalyticmetal component. Within this range, greater than or equal to about 2.5wt % of the platinum is preferred, with greater than or equal to about 5wt % more preferred. Also within this range, less than or equal to about20 wt % of platinum is preferred.

The support materials can include those materials listed above withrespect to oxidation catalyst 14. Preferably, the support materials forthe reformer 24, include, but are not limited to, hexaaluminates,aluminates, aluminum oxides (e.g., gamma-aluminum oxide, theta-aluminumoxide, delta-aluminum oxide), gallium oxides, zirconium oxides andtitanium oxides. Since the reformer is generally subjected totemperatures greater than or equal to 1,000° C., the reformer support ispreferably a hexaaluminate. Hexaaluminates are crystalline, porousstructures that are able to withstand high temperatures, e.g.,temperatures of about 1,000° C. to about 1,350° C., without sintering.Even at temperatures of up to about 1,600° C., hexaaluminates can have asurface area as high as 20 square meters per gram (m²/g).

The reformer substrate is preferably capable of operating attemperatures less than or equal to about 1,400° C.; capable ofwithstanding strong reducing environments in the presence of watercontaining, for example, hydrocarbons, hydrogen, carbon monoxide, water,oxygen, sulfur and sulfur-containing compounds, combustion radicals,such as hydrogen and hydroxyl ions, and the like, and carbon particulatematter; and has sufficient surface area and structural integrity tosupport the desired catalytic metal component and support material. Thereformer porous substrate preferably does not have a glass protectivelayer, because various reducing agents and hydroxyl groups vaporizeglass components such as phosphates, silicates as well as othermaterials such as metals, graphite, carbides and nitrides.

Materials that can be used as the reformer substrate include, zirconiumtoughened aluminum oxide, titanium toughened aluminum oxide, aluminumoxide, zirconium oxide, titanium oxide, as well as oxides, alloys,cermets, and the like, as well as combinations comprising at least oneof the foregoing materials. Preferred materials for the reformersubstrate are aluminum oxide, zirconium oxide, and combinationscomprising aluminum oxide and zirconium oxide.

Referring now to FIG. 4, an exemplary exhaust treatment system generallydesignated 400 is illustrated. As briefly mentioned above, the number ofcomponents in a system may vary. In this system, two NO_(X) adsorbers 18are arranged in a parallel configuration with each fluid pathway mergingat a SCR catalyst 20 disposed downstream. In other words, the by-passconduit shown in FIG. 3 was replaced with and additional NO_(X) adsorber118. In this embodiment, fluid flow along a given pathway may bedetermined by valve 30, as discussed above. Similarly, reductant flowmay be controlled by valve 38. Each NO_(X) adsorber 18, 118 and SCRcatalyst 20 may be regenerated as described above. More particularly, afirst NO_(X) adsorber 18 is taken “off-line”, i.e., exhaust fluid isby-passed around it to the second NO_(X) adsorber 118. At the same time,reformate (e.g., primarily hydrogen and carbon monoxide), i.e., areductant, is then introduced into reformate conduit 32, which is influid communication with both first and second NO_(X) adsorber 18, 118.Depending on which NO_(X) adsorber 18, 118 is “off-line”, valve 38 willintroduce reformate to that “off-line” NO_(X) adsorber 18, 118. Thecarbon monoxide reductant consumes oxygen, the air to fuel ratiodecreases to less than or equal to about 12, and the reductant hydrogenreacts with NO_(X) in the NO_(X) adsorber 18 producing the reductantammonia. The reductant ammonia then collects in SCR catalyst 20 locateddownstream from the first and the second NO_(X) adsorber 18, wherein theSCR catalyst 20 may store the reducing agent as ammonia or ammoniumhydroxide. The ammonia may than be used to react with NO_(X) slip pastNO_(X) adsorbers 18, 118.

Examples of this reaction are as follows:2NO+2NH₃+½O₂→2N₂+3H₂O  (IV)NO+NO₂+2NH₃→2N₂+3H₂O  (V)

FIG. 4 also illustrates a second oxidation catalyst 36, which is capableof oxidizing CO and NH₃, disposed down stream of the SCR catalyst 20.This catalyst may be used, for example, to oxidize any carbon monoxide(CO), ammonia (NH₃), nitrous oxide (N₂O) and/or hydrogen sulfide (H₂S)passing through the SCR catalyst 20 into carbon dioxide (CO₂), nitrogen(N₂), sulfur dioxide (SO₂), and water (H₂O). The second oxidationcatalyst 36 may comprise similar materials as discussed in relation tofirst oxidation catalyst 14.

In various embodiments, the second oxidation catalyst 36 may furthercomprise a zeolite capable of oxidizing NH₃, e.g., the zeolite may bepresent in an amount greater than or equal to about 20 wt % zeolite as asupport material, based upon the total weight of the underlayer.Preferably, the zeolite is an underlayer disposed over the substrate,with a catalyst overlayer disposed over the underlayer. The zeoliteunderlayer can have a zeolite loading of about 0.1 g/in³ (about 0.006g/cm³) to about 1.5 g/in³ (about 0.9 g/cm³), with about 0.25 g/in³(about 0.02 g/cm³) to about 0.75 g/in³ (about 0.05 g/cm³) preferred. Theoverlayer can have catalytic metal component loading of about 1.0 g/in³(about 0.06 g/cm³) to about 5.0 g/in³ (about 0.3 g/cm³), with about 2.5g/in³ (about 0.15 g/cm³) to about 4.0 g/in³ (about 0.24 g/cm³).

The ratio of the zeolite to other catalytic metal materials may be about80:20 to about 20:80. The zeolite layer is preferably catalytic metalfree (i.e., catalytic metal component was not added to the zeolite priorto application to the substrate). Separating the catalytic metalcomposition from the zeolite helps eliminate adverse interactionsbetween highly acidic catalyst metal solutions and the zeolite material.This separation prevents leaching of aluminum from the zeolitestructure, thus improving the durability of the zeolite as well aspreserving catalyst metal dispersion.

The zeolites preferably have the following characteristics: (1) capableof adsorbing hydrocarbon preferentially over water when exposed toexhaust gas streams at temperatures under cold start conditions to about800° C.; (2) preferably have a heat of adsorption value of greater thanor equal to about 9.5 kilocalories per gram (kcal/g) of hydrocarbon atabout 150° C.; (3) capable of withstanding accelerated aging conditions,such as exposing a zeolite coated substrate to temperatures of about600° C. for greater than or equal to about 50 hours on an enginedynamometer, while still retaining both its adsorption properties andits structural integrity.

The zeolite preferably has a silicon to aluminum (Si/Al) molar ratio ofgreater than or equal to about 12, a Na content less than or equal toabout 0.1 wt. % and an average pore size (measured along the majordiameter) of about 0.1 nanometer (nm) to about 1.0 nm. Zeolite typesinclude Y-type, beta-type, ZSM-5, mordenite, ferrierite, faujisite, andthe like, which can efficiently adsorb hydrocarbons having majormolecular diameters of less than or equal to about 0.4 nm. Preferably,the zeolite is a Y-type zeolite such as large pore zeolite (e.g.,zeolite Y, ultra stable zeolite Y, de-aluminated zeolite Y, and thelike), preferably with an average pore size of about 0.3 nm to about 0.5nm (e.g., about 0.4 nm), a silica to alumina ratio of greater than orequal to about 100, and a Na content of less than or equal to about 0.01wt. % based on the total weight of the zeolite.

The oxidation catalyst 36 can further comprise non-zeolite support(s) inaddition to the zeolite. Preferable supports include alkaline earthcoated aluminum oxide, zirconium oxide, titanium oxide, and the like, aswell as combinations comprising at least one of the foregoing, withtitanium-zirconium solid solutions preferred. The support can alsocomprise a rare earth material selected from scandium, yttrium,lanthanum, cerium, praseodymium, neodymium, dysprosium, ytterbium, andthe like. All or a portion of the rare earth materials can beco-deposited from solutions with the catalytic metal components. Thesupport oxides-rare earth oxides have the catalyst metals deposited and“fixed” through calcination prior to being mixed or layered with thezeolite. Preferably, the second oxidation catalyst catalytic metalcomponent comprises palladium, platinum, and/or rhodium, and mixturesand alloys of palladium, platinum and rhodium. Preferably, the catalyticmetal component is palladium

In addition to those components shown if FIG. 4, additional SCR catalystmay be added downstream of the NO_(X) adsorber 18. Preferably, theadditional SCR catalysts are arranged in a parallel configurationsimilar to the NO_(X) adsorber 18. The parallel configuration allowsselective regeneration of the SCR catalyst 20.

In addition to the various exhaust emission treatment devices, thesystem can comprise various sensor(s). For example, an oxygen sensor, aNO_(X) sensor, and/or a NH₃ sensor may be located downstream of NO_(X)adsorber 18 and/or SCR catalyst 20 to monitor NO_(X) and NH₃ slipthrough a given system component. A temperature sensor can be disposedupstream and adjacent to the oxidation catalyst 14.

It is noted that FIGS. 3 and 4 illustrate embodiments where the sourceof NO_(X) for ammonia generation is the NO_(X) stored in the NO_(X)adsorbers 18. As described above, the ammonia produced is then stored inthe SCR catalyst 20, where it is used to reduce NO_(X) present in theexhaust fluid. However, in other embodiments (FIGS. 5-7), the system maynot comprise a NO_(X) adsorber. In such systems, ammonia is produced“off-line”, i.e., not within the exhaust fluid stream. This ammonia maythen be introduced into the system via exhaust conduit 22, for example,upstream of the SCR catalyst 20, wherein the ammonia is stored in theSCR catalyst 20. The stored ammonia may then be used to react withNO_(X) present in the exhaust fluid. The SCR catalyst 20 may beregenerated by introducing ammonia into the exhaust fluid as describedherein. Regeneration may be based on factors like NO_(X) slip, engineschedule, time, or a combination of the foregoing.

Referring now to FIG. 5, an exemplary exhaust treatment system generallydesignated 500 is illustrated. The system 500 comprises a fuel supplysource 26 in fluid communication with reformer 24 and burner 38. Airsource 46 is in fluid communication with burner 38. A flame arrester 40may be disposed between burner 38 and reformer 24 (i.e., downstream ofburner 38 and upstream of reformer 24). Burner 38 is in fluidcommunication with reformer 24 and is located upstream of and in fluidcommunication with mixing chamber 42. Mixing chamber 42 is locatedupstream of and in fluid communication with reactor 44. Within thissystem valves 48, 50, and 52 may be added between various components tocontrol the fluid flow from that given component. For example, valve 48may be disposed between burner 38 and mixing chamber 42 to control fluidflow from burner 38 to mixing chamber 42.

Burner 38 and reformer 24 are both preferably in direct fluidcommunication with mixing chamber 42. Additionally, reformer 24 is inselective fluid communication with oxidation catalyst 14 and particulatefilter 16 via valve 28. In other words, reformate may be suppliedintermittently to oxidation catalyst 14 and/or particulate filter 16 toregenerate these components, and/or reformate may be supplied to mixingchamber 42 via valve 52 to be used in the production of ammonia.Accordingly, the system offers the advantage of on-board regeneration ofammonia using an available fuel source 26, as well as selectiveregeneration of oxidation catalyst 14 and particulate filter 16.

The burner 38 is one where a fuel source 26 is mixed with an oxidant,e.g., air from the atmosphere through air source 46 or exhaust gasrecirculation (EGR) through air source 46, and burned to producenitrogen oxides (NO_(X)), which are then fed to the mixing chamber 42,to the reformer 24 via a flame arrestor 40, and/or are used to heat apassenger compartment prior to introduction into the exhaust conduit 22.Additionally, EGR may be fed directly to the reformer. In FIG. 5, an EGRsource 45 is shown to schematically illustrate this embodiment. When EGRis used in the reformer, EGR is diverted to the off-line reformer via,for example, a valve disposed downstream of the SCR catalyst 20. It isnoted that when EGR is used in the reformer, the reformer may water gasshift water present in the EGR to hydrogen. It is further noted that theEGR diluent can decrease the combustion rate, thereby reducing thereforming temperature and increasing the partial oxidation products. Theburner 38 may be used for the combustion of a mixture of air and fuel inany desired ratio. It is preferable to feed the air and the fuel intothe burner 38 in an air to fuel ratio of about 14 to about 70. Withinthis range, it is generally desirable to use an air to fuel ratiogreater than or equal to about 18, preferably greater than or equal toabout 22, and more preferably greater than or equal to about 30. Alsodesirable within this range, is an air to fuel ratio of less than orequal to about 65 preferably less than or equal to about 60, and morepreferably less than or equal to about 50.

The mixing chamber 42 is a vessel having an inlet port 54 for thereformate from the reformer 24, as well as an inlet port 56 for theNO_(X) generated in the burner 38. The mixing chamber 42 is equippedwith a device and/or geometry for facilitating the mixing of thereformate with NO_(X) such as a stirrer, baffles, and the like. Themixing chamber 42 may optionally be fitted with a cooling device tofacilitate mixing and to obtain preferred catalyst operatingtemperatures for the fluids prior to entry into the reactor 44. In anexemplary embodiment, the mixing chamber 42 is used to facilitate theremoval of any free oxygen present in the reformate and burner effluent.The free oxygen may be removed by exposure to a catalyst bed comprisingmetals such as iron, vanadium, ruthenium or tungsten, which areconverted to metal oxides upon exposure to free oxygen.

The NO_(X) generated in the burner 38 and the reformate generated in thereformer 24 are generally fed into the mixing chamber 42 in any desiredratio and at a temperature effective to facilitate an intimate mixing ofthe gases. It is generally desirable to feed the NO_(X) and reformatsinto the mixing chamber 42 in a NO_(X) to reformate ratio of about 2 toabout 0.08. Within this range, it is generally desirable to have aNO_(X) to reformate ratio of less than or equal to about 1, preferablyless than or equal to about 0.5, and more preferably less than or equalto about 0.25. Also desirable within this range is a NO_(X) to reformateratio of greater than or equal to about 0.09, preferably greater than orequal to about 0.1, and more preferably greater than or equal to about0.125.

The reactor 44 receives a mixture of the NO_(X) and the reformate fromthe mixing chamber 42 preferably at a temperature of about 220° C. toabout 400° C. The reactor 44 comprises a metal shell around an ammoniaforming catalyst that facilitates a reaction between NO_(X) and thehydrogen to yield ammonia. The ammonia forming catalyst metal is loadedon a catalytic metal support, or “washcoat”. The ammonia formingcatalyst can be a type that stores either the reformate generated in thereformer 24 until NO_(X) is available or it could store the NO_(X)generated from the burner 38 until the reformate is available. It is,however, desirable to use an ammonia forming catalyst that stores NO_(X)until the reformate is available, since a lower volume of catalyst isused for NO_(X) storage and the ensuing reaction.

In various embodiments, reactor 44, shown in FIG. 5 for example, may bea three-way conversion catalyst. It is noted that a three-way conversioncatalyst has typically been used to oxidize hydrocarbons and carbonmonoxide, and reduce NO_(X). The term “three-way” is not being usedherein to describe the function of a catalyst to treat hydrocarbons,carbon monoxide, and NO_(X), but rather to describe the catalyst itself.In other words, the three-way conversion catalyst may be referred simplyas a reactor capable of producing ammonia. However, it is noted if thethree-way catalyst disclosed herein were disposed in-line, it could alsobe used to treat hydrocarbons, carbon monoxide, and NO_(X).

The reactor 44 generally comprises a substrate, a catalyst metal(s), andcatalyst support material, which may be similar to the relating elementsof the various exhaust treatment devices discussed above. For example,the catalyst metal support may comprise refractory oxides such asaluminum oxides, stabilized aluminum oxides such as barium stabilizedaluminum oxide, zirconium, yttrium oxide rare earth oxides such ascerium, lanthanum praseodymium, neodymium or ytterbium oxide, transitionmetal oxides such as nickel, manganese, cobalt copper or iron oxide andengineered materials such as zeolites, as well as mixtures such ascerium-zirconium solid solutions and the like.

The reactor 44 may further comprise NO_(X) adsorbing elements such asbarium oxide and/or cesium oxide in an amount of about 2 to about 12 wt%, based on the total weight of the catalytic metal and catalytic metalsupports. The catalyst metal generally comprises a precious metal suchas platinum, palladium, rhodium, ruthenium, and the like, as well ascombinations comprising at least one of the foregoing metals. In anexemplary embodiment, the ruthenium may be present in a loading of about0.11 g/in³ (about 0.007 g/cm³) to about 0.40 g/in³ (about 0.02 g/cm³)while the platinum, palladium or rhodium may be present in loading ofabout 0.011 g/in³ (about 0.0007 g/cm³) to about 0.046 g/in³ (about 0.003g/cm³).

Preferably, the catalytic metal(s) of the reactor 44 comprises acombination of ruthenium with other metals. The other metals, e.g.,rhodium, and the like, can be present in an amount less than theruthenium. In the case of a ruthenium-rhodium combination, the preciousmetal component can comprise up to about 99 wt % ruthenium and up toabout 4.0 wt % rhodium, based on the total weight of the catalytic metalcomponent. Within this range, greater than or equal to about 0.2 wt % ofrhodium is preferred, with greater than or equal to about 1.0 wt %rhodium more preferred. Also within this range, less than or equal toabout 2.0 wt % of rhodium is preferred, with less than or equal to 1.2wt % rhodium more preferred.

In an exemplary embodiment related to the functioning of the reactor 44,any traces of free oxygen present in the reactor 44 are first removedaccording to the reaction (VI). This reaction generally occurs beforeany NO_(X) is reduced:H₂+CO+O₂→CO₂+H₂O  (VI)Following the removal of oxygen, ammonia can be formed by reducingNO_(X) according to the following reactions (VII) and (VIII):5H₂+2NO→2NH₃+2H₂O  (VII)7H₂+2NO₂→2NH₃+4H₂O  (VIII)From the reactions (VII) and (VIII) it may be seen that 1 mole of eitherNO or NO₂ is used to generate 1 mole of ammonia. If the hydrogenreducing atmosphere is not present in the appropriate quantities asrepresented by the reactions (VII) and (VIII) respectively, partiallyreduced species can also form according to the reactions (IX) and (X):H₂+2NO→N₂O+H₂O  (IX)3H₂+2NO₂→N₂O+3H₂O  (X)These partially reduced species are undesirable, and in order to preventtheir formation, it is preferred to use an excess of hydrogen tofacilitate the conversion of (NO_(X)) according to the reactions (XI)and (XII):6H₂+2NO→2NH₃+2H₂O+H₂  (XI)8H₂+2NO₂→2NH₃+4H₂O+H₂  (XII)

From reactions (XI) and (XII), it may be seen that if the NO_(X) is 100%NO, then about 3 moles of H₂ are used to convert every mole of NO toammonia. If the NO_(X) is 100% NO₂, then about 4 moles of H₂ are used toconvert every mole of NO₂ to ammonia. Since the NO_(X) from the burner38 is usually a mixture of NO and NO₂, it is generally desirable to usean amount of about 3 to about 4 moles of H₂ to facilitate the conversionto ammonia. If less than 4 moles of H₂ is used, however, a portion ofthe NO_(X) may pass through the exhaust system without being convertedto ammonia. This is generally termed “NO_(X) slip”. In order to preventsuch NO_(X) slip, it is preferable to use an amount of greater than orequal to about 4 moles of H₂ per mole of NO_(X).

The conditions within the reactor 44 are preferably controlled to have atemperature and pressure effective to facilitate the ammonia producingreaction. The reaction to produce ammonia in the reactor 44 generallyoccurs at a temperature of about 120° C. to about 400° C. Within thisrange, it is generally desirable to conduct the reaction at atemperature of greater than or equal to about 180° C., preferablygreater than or equal to about 220° C., and more preferably greater thanor equal to about 240° C. Also desirable within this range, is atemperature of less than or equal to about 400° C., preferably less thanor equal to about 320° C., and more preferably less than or equal toabout 280° C. The pressure is generally about 15 kilopascals (kPa) toabout 150 kPa. Within this range, it is generally desirable to conductthe reaction at a pressure of greater than or equal to about 30 kPa,preferably greater than or equal to about 45 kPa, and more preferablygreater than or equal to about 60 kPa. Also desirable within this rangeis a pressure of less than or equal to about 150 kPa, preferably lessthan or equal to about 120 kPa, and more preferably less than or equalto about 90 kPa.

Ammonia produced in reactor 44 may be introduced upstream of SCRcatalyst 20. As described above, the ammonia may be stored in the SCRcatalyst. The NO_(X) in the exhaust stream generally reacts with thestored ammonia in SCR catalyst 20. In an exemplary embodiment, it isgenerally desirable to maintain the SCR catalyst 20 at a temperature ofless than or equal to about 480° C. This generally prevents thedecomposition of ammonia to form nitrogen oxides, which are undesirable.

Referring now to FIG. 6, an exemplary exhaust treatment system generallydesignated 600 is illustrated. FIG. 6 is included to illustrate variousadditional embodiments envisioned. For example, a second fuel source 58may be included in the system 600 in fluid communication with burner 38.As such, second fuel source may employ substantially the same fuel asfuel source 26 or alternatively it may employ a different fuel. Examplesof the fuel source 58 include hydrocarbon fuels such as gasoline,diesel, ethanol, methanol, kerosene, and the like; gaseous fuels, suchas natural fluid, propane, butane, and the like; and alternative fuels,such as hydrogen, biofuels, dimethyl ether, and the like; and the like,as well as combinations comprising at least one of the foregoing fuels.The selection of fuel source 58 is based upon application, expense,availability, and environmental issues relating to the fuel source 58.The preferred fuel source is diesel. Alternatively to the additionalfuel source 58, fuel source 26 could be disposed in fluid communicationwith the burner 38.

FIG. 6 further illustrates schematically that heat generated from burner38 may be used in a heating device 64 for heating a passengercompartment of a vehicle. Valves 60 and 62 may be disposed in fluidcommunication with burner 38 to regulate flow of fluid from burner 38.The fluid from the burner comprising NO_(X) may be diverter to heatingdevice 64 via valve 60, wherein the fluid may then be deposited inexhaust conduit 22 upstream of SCR catalyst 20, or into the reactor 44via the optional mixing chamber 42. Preferably, the fluid (effluent)from burner may be disposed upstream of NO_(X) adsorber 18, which is indirect fluid communication with SCR catalyst 20. Alternatively, thefluid from burner 38 may be diverted to mixing chamber 42 via valve 48.Optional mixing chamber 42 is disposed upstream and in fluidcommunication with reactor 44. Accordingly, as discussed above, theNO_(X) from the burner may be used to produce ammonia in the reactor 44.Additionally, the burner effluent may be diverted to the reformer 24 viavalve 50 and a flame arrestor 40. The reformate exiting the reformer 24may be disposed upstream of oxidation catalyst 14, diesel particulatefilter 16, NO_(X) adsorber 18, and/or SCR catalyst 20. Preferably, thereformate is selectively disposed via valve 28 directly before oxidationcatalyst 14 into exhaust conduit 22, directly before particulate filter16 into exhaust conduit 22, or directly before NO_(X) adsorber 18 intoexhaust conduit 22.

Additionally, in other embodiments, a NO_(X) adsorber 18 may be disposedin fluid communication with reactor 44. Preferably, the NO_(X) adsorber18 is disposed upstream of the SCR catalyst 20 in direct fluidcommunication with the SCR catalyst 20. Valve 66 is in fluidcommunication with reactor 44 to selectively control fluid flow fromreactor 44 to NO_(X) adsorber 18 and/or SCR catalyst 20. In addition tothe configurations illustrated individually in FIGS. 1-5, combinationsof these embodiments are also envisioned. For example, additional NO_(X)adsorber 118 may be included in parallel, or series within the system.

In an exemplary embodiment, engine 12 is in direct fluid communicationwith and disposed upstream of oxidation catalyst 14; oxidation catalyst14 is in direct fluid communication with and disposed upstream ofparticulate filter 16; particulate filter 16 is in direct fluidcommunication with and disposed upstream of NO_(X) adsorber 18; NO_(X)adsorber 18 is in direct fluid communication with and disposed upstreamof SCR catalyst 20; and SCR catalyst 20 is in direct fluid communicationwith and disposed upstream of second oxidation catalyst 36. In otherwords, engine 12 is in serial fluid communication with, oxidationcatalyst 14, particulate filter 16, NO_(X) adsorber 18, and SCR catalyst20.

FIG. 7 is a schematic illustration of an exhaust treatment systemgenerally designated 700. This figure is included to illustrate yetanother method of on-board generation of ammonia. This embodiment issimilar to those illustrated in FIGS. 5 and 6 in that efforts are madeto generate NO_(X) off-line for the purposes of using the NO_(X) toproduce ammonia. As will be discussed in greater detail, this systemillustrates an embodiment where fuel, e.g., diesel fuel is“nitrogenized” prior to entering a reformer. This nitrogen enriched fuelmay be used to produce high levels of NO_(X) and/or high levels ofammonia. The term “high” as used in relation to this embodiment relatesto NO_(X) and/or ammonia concentration of greater than or equal to about1,000 parts per million (ppm), with greater than 2,000 ppm preferred,wherein the parts per million is a volumetric percentage.

In comparison, a diesel engine 12 generally produces NO_(X) in aconcentration of less than or equal to about 10 ppm. This type of NO_(X)may generally be characterized as “fuel NO_(X)”. The term “fuel NO_(X)”as used herein refers to NO_(X) released from fuel when it is burned,i.e., the NO_(X) released may also be a function of the fuel type used.For example, biomass may have a higher nitrogen content compared todiesel fuel, as such a greater volume of NO_(X) would comparatively begenerated from the biomass than diesel fuel. The term “thermal NO_(X)”as used herein generally refers to NO_(X) generated as a result ofoperating temperatures, e.g., temperatures greater than or equal toabout 900° C., i.e., nitrogen in the air reacts with oxygen to formNO_(X). Thermal NO_(X) may be produced in a concentration of less thanor equal to about 1000 ppm, with about less than or equal to about 400ppm common. Additionally, NO_(X) may be characterized as “promptNO_(X)”. The term “prompt NO_(X)” is used herein to describe theinteraction of atmospheric nitrogen and carbon in the fuel. Accordingly,a fuel may be purposely “nitrogenized”, i.e., nitrogen is added to thefuel, to increase the NO_(X) produced in the system. Prompt NO_(X) maybe produced in an amount less than or equal to about 10 ppm.

In the system 700, air from air source 46 is introduced into permeablemembrane 70, wherein the membrane is capable of inhibiting passage ofoxygen, thereby producing a ratio of oxygen to nitrogen in an outputstream 72 of the permeable membrane 70. Generally, air comprises about21 volume percent (vol %) oxygen, and about 79 vol % nitrogen. Theoutput stream preferably comprises about 5 vol % oxygen to about 10 vol% oxygen and about 90 vol % nitrogen to about 95 vol % nitrogen. Assuch, a volume ratio of oxygen to nitrogen is preferably about 1:9 toabout 1:19.

Referring now to FIG. 7, the system 700 comprises a permeable membrane70 in direct fluid communication with a reformer 82. The oxygen tonitrogen ratio is controlled by the permeable membrane 70 as discussedabove and introduced into reformer 82. Reformer 82 is capable of mixingthe output stream 72 of permeable membrane 70 with fuel from fuel source26. The reformer 82 is designed to withstand operating conditionsfavorable for the production of ammonia from the fuel source. Forexample, the operating pressure is sufficient to produce ammonia at theoperating temperature. The pressure may be less than or equal to about100 atmosphere, with an operating pressure of about 20 atmosphere to 40atmosphere generally employed. An operating temperature of the reformer82 is sufficient to produce ammonia at the operating pressure, andpreferably less than or equal to about 300° C. Ammonia produced inreformer 82 maybe disposed upstream of SCR catalyst 20 via valve 84.Advantageously, valve 84 is capable of selectively controlling fluidcommunication between reformer 82 and SCR catalyst 20. As such, ammoniamay be intermittently introduced into SCR catalyst 20 to regenerate theSCR catalyst 20.

Reformer 82 may comprise a catalytic metal component, support material,and substrate. This reformer 82 may have an optional mixing chambercoupled to it and is preferably encased in a pressure controlledcontainer. The mixing chamber allows the air from permeable membrane 70and the fuel from fuel source 26 to mix prior to entering the reformer82. Additionally, reformer 82 comprises catalyst materials, supportmaterials substantially the same as reformer 24. Preferably, in variousembodiments reformer 82 comprises an iron oxide catalyst metal and/orosmium.

In various embodiments disclosed herein, the system does not comprise aNO_(X) adsorber(s), which may be used to trap NO_(X) during leanoperating conditions, i.e., when the air-to-fuel ratio is greater thanthe balanced combustion stoichiometry. For example, the air-to-fuelratio is greater than about 14.7 and may be between about 19 to about35. While NO_(X) may not be trapped and later reduced, NO_(X) present inan exhaust fluid may be reduced to nitrogen using ammonia stored on theSCR catalyst as discussed above. Conversion of greater than or equal toabout 90% of the NO_(X) present in the exhaust fluid to nitrogen may beobtained, with greater than about 95% preferred, wherein the percentsused herein refer to volumetric percentages. These high conversions ofNO_(X) may be obtained by regulating a ratio of NO to NO₂ in the exhaustfluid. Preferably, the ratio of NO to NO₂ in the exhaust fluid is about1:0.6 to about 1:1.5, with a ratio of about 1:1 especially preferred. Assuch, a portion of NO may be converted to NO₂ in order to obtain thedesired ratio, e.g., 1:1. In an exemplary embodiment, a non-thermalplasma (NTP) reactor(s) may be used to convert a portion of NO to NO₂.

The NTP reactor can comprise several kinds of configurations, includingan electrified packed bed reactor, a glow-discharge plasma reactor, acorona discharge reactor, a RF discharge reactor, a pulsed coronareactor, a dielectric-barrier discharge reactor, surface dischargereactor, or the like, as well as combinations comprising at least one ofthese types of reactors. A non-thermal plasma can be generated byseveral methods, such as electrical fields, electron beams, andirradiation with electromagnetic energy of appropriate intensity andwavelength, with generation by electrical fields desirable. Preferably,a flat plate dielectric barrier type reactor is used. Exemplarynon-thermal plasma reactors are disclosed, for example, in U.S. PatentPublication Nos. 20030182930 A1 to Goulette et al., and 20030150709 A1to LaBarge et al., U.S. Pat. Nos. 6,423,190, 6,464,945, and 6,482,368 toHemingway et al., and U.S. Pat. No. 6,638,484 to Nelson et al., whichare incorporated herein by reference.

In order to attain the desired NO₂ yield from the non-thermal plasmareactor, the power to the reactor, the electric field strength, and/orthe temperature of the incoming gases can be controlled. The non-thermalplasma reactor may be controlled by varying the power applied to theincoming gasses (e.g., measured in joules/liter). In addition to thepower, the electrical field strength within the discharge zone of thereactor can be controlled. Additionally, the temperature of the incominggasses from the reformer is preferably about 100° C. to about 600° C.

Advantageously, a non-thermal plasma reactor is capable of obtaining aNO to NO₂ ratio of about 1:0.6 to about 1:1.5 at temperatures below 200°C. Types of non-thermal plasma reactors may include but are not limitedto, a dielectric barrier or silent discharge type, a pulsed coronareactor, packed bed reactor such as a ferroelectric bed reactor, and asurface discharge reactor.

In this exemplary embodiment where the NO to NO₂ is about 1:1, thereactions within the SCR catalyst may be characterized by the followingequations:5H₂+2NO→2NH₃+2H₂O  (XIII)4NH₃+4NO₂→4N₂+6H₂O+O₂  (XIV)

Turning now to FIG. 8, an exemplary exhaust treatment system generallydesignated 800 is illustrated. The system 800 comprises a non-thermalplasma reactor 86 disposed in fluid communication with engine 12. SCRcatalyst 20 is disposed in fluid communication with and down stream ofnon-thermal plasma reactor 86. A reformer 24 is in selective fluidcommunication with SCR catalyst 20. Reformate from the reformercomprising hydrogen may be used to regenerate the SCR catalyst 20.Various other embodiments are envisioned, as discussed throughout,wherein ammonia is produced to regenerate the SCR catalyst 20.

In operation, an exemplary method of treating an exhaust fluid, maycomprise, e.g., introducing an exhaust fluid to an oxidation catalyst12. The oxidation catalyst is capable of partially oxidizing greaterthan or equal to 60 vol. % hydrocarbon present in an exhaust fluid, withgreater than or equal to about 75 vol. % preferred, with greater thanabout 85% more preferred, and greater than or equal to about 95 vol. %even more preferred. Traditionally, an oxidation catalyst has been usedto fully oxidize greater than or equal to 99 vol. % hydrocarbons in anexhaust stream entering the oxidation catalyst. In other words, theoxidation catalyst disclosed herein preferably acts to partially oxidizehydrocarbons, whereas traditional oxidation catalysts act to fullyoxidize hydrocarbons. This oxidation catalyst, for example, can comprisea honeycomb substrate with about 300 to about 500 cells/in². On thesubstrate is an acidic, solid solution support with a catalystcomprising precious metal(s), wherein a catalyst comprising ruthenium ispreferred. The solid solution can be a titanium-zirconium solution.

The exhaust fluid may then be introduced to a particulate filter 16.Preferably, the particulate filter comprises a WGS catalyst that may beused to convert carbon monoxide and water into hydrogen and carbondioxide, thereby increasing the amount of reducing agents present in theexhaust fluid. Traditionally, the catalyst employed in a particulatefilter has been used primarily as a traditional oxidation catalyst(e.g., to fully oxidize hydrocarbons). For example, in a traditionalcatalytic particulate filter, an exhaust stream comprising about 20 vol.% hydrogen entering the filter will have about 12 vol. % volume percenthydrogen exiting the filter based upon the total volume of the exhauststream. In contrast, all else being equal, a WGS particulate filter asdisclosed herein maintains (e.g., within ±2 vol. %) or increases thehydrogen concentration of the stream, e.g., preferably has greater thanor equal to about 20 vol. % hydrogen exiting the filter, with greaterthan or equal to 22 vol. % preferred, with greater than or equal toabout 26 vol. % more preferred, based upon the total volume of theexhaust stream.

The exhaust stream from the particulate filter (i.e., filter effluent)may then be introduced to a NO_(X) adsorber 18. Under the operatingconditions disclosed herein the NO_(X) adsorber 18 may be used toproduce greater than or equal to about 5,000 ppm NH₃ (e.g., about 1 vol.%) based upon the total volume of the NO_(X) effluent, with greater thanor equal to about 10,000 ppm preferred. In contrast to the presentadsorber, a traditional NO_(X) adsorber generally produces less than orequal to 5 ppm NH₃, when hydrocarbons are directly injected into theexhaust stream. The NO_(X) adsorber 18 preferably comprises a basicsupport, e.g., a basic solid solution on an about 900 to about 1,300cells/in² substrate, preferably comprising corderite, with a protectivecoating (e.g., phosphate(s)) between the substrate and the catalystmetal composition. For example an alkaline earth solid solution (e.g.,barium oxide-zirconium solid solution) optionally with some alumina(e.g., about 2 to about 3 wt % alumina, based upon the total weight ofthe support), can be employed.

The ammonia produced may then be stored in the SCR catalyst 20 storesammonia and selectively reacts the stored ammonia species with NO_(X) inthe exhaust stream The SCR catalyst 20, for example, can have asubstrate comprising a ceria or tungsten. Here the support is acidic toenable the adsorption of the NH₃. Therefore, an acidic solid solution ispreferred, such as a zirconium-titanium solid solution. A possiblecatalyst disposed on the support is palladium-ruthenium.

Advantageously, each and every embodiment disclosed herein allows foron-board generation of ammonia. For example, in one exemplaryembodiment, NO_(X) trapped in NO_(X) adsorber may be used to generateammonia, while regenerating the NO_(X) adsorber(s). The ammoniagenerated may then be used to regenerate the SCR catalyst(s) and reduceNO_(X) in the exhaust fluid that is diverted around the NO_(X) adsorberduring the regeneration phase.

Depending on the particular system architecture, the system may includean optional heat exchanger (not shown) to reduce the reformatetemperature.

The heated reformate can be used to regenerate catalysts, e.g., vaporizethe oil derived metal phosphate glaze(s) and re-disperse the catalyticmetals. For example, in system 100, valve 28 is opened allowing hydrogenand carbon monoxide from the reformer 24 to be fed directly to theexhaust fluid stream entering the oxidation catalyst 14, and particulatetrap 16. For example, organometallic zinc and calcium phosphates (e.g.,zinc dialkylphosphate (ZDP)) vaporized from engine oil are deposited asdiffusion limiting “glassy” phases, e.g., CaPO₄, Zn₃(PO₄)₂, Ca₂P₂O₆,Ca₂P₂O₇, Ca(PO₃)₂, Zn₂P₂O₇, mixed CaZnP₂O₆, and the like. These denseglass phases deposited over the catalysts, and in the particulate trappores. Hydrogen and carbon monoxide reducing agents in the presence ofsteam and/or hydroxyl radicals vaporize the glassy phases. The vaporizedphosphate “glazes” can be re-deposited downstream as innocuousparticulate phosphates (e.g., non-glassy).

The systems disclosed herein apply a different philosophy to attain alow emissions exhaust gas, particularly in a diesel engine exhaust.These systems do not attempt to attain complete oxidation of the variousexhaust gas constituents at each stage of the system. To the contrary,the components are designed to partially oxidize the variousconstituents so that the partially oxidized constituent can be employeddownstream in another treatment device, thereby enhancing the overallremoval of contaminants from the exhaust stream. An advantage of seekingpartial oxidation is that the desired efficiency of the variouscatalysts and the amount of various precious metals employed are bothreduced. These systems employ ammonia in NO_(X) reduction, while, inother systems, e.g., a typical converters (i.e., three-way, oxidation,particulate trap oxidation and NO_(X) adsorbers), any ammonia in astream would be rapidly oxidized to water and primarily N₂O, with smallamounts of NO₂ and NO. Previously, ammonia would not intentionally beformed from the NO_(X) (e.g., NO_(X) stored in a NO_(X) adsorber), andwould not be used as taught herein.

While the invention has been described with reference to an exemplaryembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

1. A NO_(X) abatement system, comprising: a first NO_(X) adsorber (18)disposed in-line, capable of being disposed downstream of and in fluidcommunication with an engine (12); a selective catalytic reductioncatalyst (20) disposed in-line, downstream of and in direct fluidcommunication with the first NO_(X) adsorber (18), wherein the selectivecatalytic reduction catalyst (20) is capable of storing ammonia; and anoff-line reformer (24) disposed in selective communication with andupstream of the first NO_(X) adsorber (18) and the selective catalyticreduction catalyst (20), wherein the reformer (24) is capable ofproducing a reformate comprising primarily hydrogen and carbon monoxide.2. The system of claim 1, further comprising a first oxidation catalyst(14) and a particulate filter (16) disposed in-line, upstream of and influid communication with the first NO_(X) adsorber (18), wherein theparticulate filter (16) comprises a water gas shift catalyst.
 3. Thesystem of claim 2, further comprising a second oxidation catalyst (36)disposed in-line, downstream of and in direct fluid communication withthe selective catalytic reduction catalyst (20), wherein the secondoxidation (36) comprises a zeolite.
 4. The system of claim 3, whereinthe second oxidation catalyst (36) comprises a zeolite under-layercomprising the zeolite, wherein the zeolite under-layer is catalyticmetal free.
 5. The system of claim 3, wherein the zeolite is present inan amount greater than or equal to about 20 wt %, based on the totalweight of the zeolite under-layer.
 6. The system of claim 3, wherein thezeolite has a Si/Al molar ratio of greater than or equal to about
 12. 7.The system of claim 2, wherein the water gas shift catalyst is capableof maintaining, within about ±2 vol %, a hydrogen concentration in anexhaust stream passing through the particulate filter (16), based upon atotal volume of hydrogen entering the particulate filter (16) comparedto a total volume of hydrogen exiting the particulate filter (16). 8.The system of claim 2, wherein the water gas shift catalyst is capableof increasing a hydrogen concentration in an exhaust stream to greaterthan or equal to about 20 vol. %, based upon a total volume of theexhaust stream exiting the particulate filter (16).
 9. The system ofclaim 1, further comprising a first oxidation catalyst (14) and aparticulate filter (16) disposed in-line, upstream of and in fluidcommunication with the first NO_(X) adsorber (18), wherein the firstoxidation catalyst (14) comprises an oxidation catalyst capable ofpartially oxidizing greater than or equal to about 60 vol. % ofhydrocarbons, based upon a total amount of hydrocarbons in an exhauststream entering the first oxidation catalyst (14).
 10. The system ofclaim 9, wherein the oxidation catalyst (14) is capable of partiallyoxidizing greater than or equal to about 75 vol % of the hydrocarbons.11. The system of claim 10, wherein the oxidation catalyst (14) iscapable of partially oxidizing greater than or equal to about 85 vol %of the hydrocarbons.
 12. The system of claim 9, wherein the oxidationcatalyst (14) comprises: a Part 1 component comprising a Part 1 supportmaterial having an agglomeration of primary particles, wherein anagglomeration size, measured along a major diameter, is about 5micrometers to about 15 micrometers, and wherein the primary particlesize is less than or equal to about 300 nanometers; and a Part 2component comprises a primary particle size of less than or equal toabout 500 nanometers and a Part 2 agglomerate size of less than or equalto about 0.5 micrometers.
 13. The system of claim 12, wherein the ratioof the Part 1 component to the Part 2 component is about 80:20 to about20:80.
 14. The system of claim 12, wherein the Part 2 componentcomprises a solid solution selected from the group consisting oftitanium-zirconium oxide, yttrium-zirconium oxide, barium-zirconiumoxide, lanthanum-titanium oxide and the like, as well as combinationscomprising at least one of the foregoing,
 15. The system of claim 1,further comprising an in-line by-pass conduit (34) capable of beingdisposed in fluid communication with the engine (12) and the selectivecatalytic reduction catalyst (20), and an in-line by-pass valve (30) influid communication with the by-pass conduit (34) and the first NO_(X)adsorber (18), wherein the by-pass valve (30) is capable of diverting anexhaust stream around the first NO_(X) adsorber (18) via the by-passconduit (34) to the selective catalytic reduction catalyst (20).
 16. Thesystem of claim 15, further comprising a second NO_(X) adsorber (118)disposed downstream of the by-pass valve (30) and upstream of theselective catalytic reduction catalyst (20) such that when the exhauststream is diverted around the first NO_(X) adsorber (18) the exhauststream passes through the 5 second NO_(X) adsorber (118) prior toentering the selective catalytic reduction catalyst (20).
 17. The systemof claim 1, further comprising: an off-line burner (38) disposedupstream of and in fluid communication with the reformer (24); and anoff-line reactor (44) in fluid communication with and disposeddownstream of the reformer (24), wherein the reactor (44) comprises anammonia forming catalyst.
 18. The system of claim 17, further comprisingan off-line heat exchange (64) device in thermal communication with apassenger compartment, wherein the heat exchange device is downstream ofand in fluid communication with the burner (38).
 19. The system of claim1, wherein the first NO_(X) adsorber (18) comprises a catalyst capableof converting adsorbed NO_(X) to ammonia.
 20. The system of claim 1,wherein the first NO_(X) adsorber (18) comprises a NO_(X) trappingmaterial and a sufficient amount of a hydrophobic material to render theNO_(X) trapping material hydrophobic.
 21. The system of claim 1, whereinthe hydrophobic material is present in an amount of about 0.1 wt % toabout 2 wt %, based on a NO_(X) combined weight.
 22. The system of claim1, wherein the reformer (24) comprises a hexaaluminate support.
 23. Thesystem of claim 1, wherein the NO_(X) adsorber (18) comprises asubstrate and a protective coating coated on the substrate, wherein theprotective coating comprises phosphate.
 24. A method of NO_(X)abatement, comprising: storing engine NO_(X) from an exhaust stream in ainitial NO_(X) adsorber (18) during a storage phase; forming reformatecomprising primarily hydrogen and carbon monoxide in an off-linereformer (24) during a regeneration phase; reacting the reformate withthe stored NO_(X) to produce greater than or equal to about 5,000 ppmammonia during the regeneration phase; and storing the ammonia in aselective catalytic reduction catalyst (20) during the regenerationphase.
 25. The method of claim 24, further comprising by-passing theexhaust stream around the initial NO_(X) adsorber (18) during theregeneration phase.
 26. The method of claim 24, further comprisingreacting NO_(X) in the by-passed exhaust stream with the stored ammonia.27. The method of claim 24, further comprising storing NO_(X) in theby-passed exhaust stream in a by-pass NO_(X) adsorber (118) during theregeneration phase, and reacting the stored by-pass NO_(X) with thereformate during a storage phase of the initial NO_(X) adsorber (18).28. The method of claim 24, further comprising reacting exhaust gasrecirculation in the reformer (24) to produce hydrogen.
 29. The methodof claim 24, further comprising filtering the exhaust stream; and watergas shifting water in the exhaust stream in a filter (14) to hydrogenprior to storing the engine NO_(X); wherein the water gas shifted streamcomprises greater than or equal to about 20 vol % hydrogen exiting thefilter, based upon a total volume of the exhaust stream exiting thefilter.
 30. The method of claim 29, wherein the water gas shifted streamcomprises greater than or equal to about 26 vol % hydrogen exiting thefilter, based upon a total volume of the exhaust stream exiting thefilter.
 31. The method of claim 24, further comprising partiallyoxidizing hydrocarbons in the exhaust stream prior to storing the engineNO_(X), wherein greater than or equal to about 60 vol. % of thehydrocarbons are partially oxidized, based upon a total volume ofhydrocarbons in the exhaust stream prior to the partial oxidation. 32.The method of claim 31, wherein greater than or equal to about 75 vol %of the hydrocarbons are partially oxidized.
 33. The method of claim 32,wherein greater than or equal to about 85 vol % of the hydrocarbons arepartially oxidized.
 34. A NO_(X) abatement system, comprising: anin-line selective catalytic reduction catalyst (20) capable of beingdisposed in fluid communication with an engine (12), wherein theselective catalytic reduction catalyst (20) is capable of storingammonia; an off-line reformer (24) in fluid communication with theselective catalytic reduction catalyst (20), wherein the reformer (24)is capable of producing a reformate (24) comprising primarily hydrogenand carbon monoxide; and an off-line reactor (44) in fluid communicationwith and downstream of the reformer (24), wherein the reactor (44)comprises an ammonia forming catalyst.
 35. The system of claim 34,further comprising an off-line burner (38) in fluid communication withand upstream of the reformer (24) and the reactor (44).
 36. The systemof claim 35, further comprising an off-line mixing chamber (42) disposedupstream of the reactor (44), downstream of and in fluid communicationwith the reformer (24), and in direct fluid communication with theburner (38).
 37. A method of NO_(X) abatement, comprising: burning fueloff-line to form burner NO_(X); forming a reformate comprising primarilyhydrogen and carbon monoxide, off-line; reacting the burner NO_(X) withthe reformate to form ammonia, off-line; storing the ammonia in anin-line selective catalytic reduction catalyst; introducing engineNO_(X) to the selective catalytic reduction catalyst (20); and reactingthe engine NO_(X) with the ammonia.
 38. The method of claim 37, whereinthe burner NO_(X) and the reformate are reacted at a temperature ofabout 120° C. to about 400° C. and a pressure of about 15 kPa to about150 kPa.
 39. The method of claim 37, further comprising periodicallyregenerating the selective reduction catalyst (20) by periodicallyforming the ammonia and periodically introducing the ammonia to theselective catalytic reduction catalyst (20).
 40. The method of claim 37,further comprising heating a passenger compartment of a vehicle with theburner NO_(X).
 41. A NO_(X) abatement system, comprising: an off-linemembrane (70) capable of inhibiting passage of oxygen through themembrane (70); an off-line reformer (82) disposed downstream of and influid communication with the membrane (70) and a fuel source (26),wherein the reformer (24) is capable of producing ammonia from fuel andnitrogen; and an in-line selective catalytic reduction catalyst (20)disposed downstream of and in fluid communication the reformer (82),wherein the selective catalytic reduction catalyst (20) is capable ofstoring ammonia and capable of receiving NO_(X) from an engine (12). 42.The system of claim 41, wherein the reformer (82) comprises a pressurecontrolled container capable of operating at a pressure of about 20atmospheres to about 100 atmospheres.
 43. The system of claim 41,wherein the pressure is about 20 atmospheres to about 40 atmospheres.44. A method of NO_(X) abatement, comprising: passing air having aninitial nitrogen concentration through a membrane (70) to form amembrane effluent having a subsequent nitrogen concentration, whereinthe subsequent nitrogen concentration is greater than the initialconcentration; mixing the membrane effluent and a fuel (26) in a mixingchamber disposed upstream of and in fluid communication with a reformer(82); introducing the mixed air and fuel into the reformer (82) toproduce a reformate comprising ammonia; periodically introducing theammonia to a selective catalytic reductive catalyst (20) to regeneratethe catalyst; and reacting the ammonia stored in the selective catalyticreductive catalyst (20) with NO_(X) in an exhaust fluid.
 45. A NO_(X)abatement system, comprising: an in-line non-thermal plasma reactor (86)capable of being disposed downstream of and in fluid communication withan engine (12); an in-line selective catalytic reduction catalyst (20)disposed downstream of and in direct fluid communication with thenon-thermal plasma reactor (86); and an off-line reformer (24) disposedupstream of and in fluid communication with the selective catalyticreduction catalyst (20).
 46. The system of claim 45, wherein thenon-thermal plasma reactor (86) is capable of controlling a ratio of NOto NO₂ in an exhaust stream from the engine, wherein the ratio can becontrolled to about 1:0.6 to about 1:1.5 at temperatures less than orequal to about 200° C.
 47. A method of NO_(X) abatement, comprising:introducing an engine exhaust stream to a non-thermal plasma reactor(86); reacting NO_(X) in the exhaust stream to form a non-thermal plasmareactor effluent having a ratio of NO to NO₂ of about 1:0.6 to about1:1.5 at temperatures of less than or equal to about 200° C.; formingreformate comprising primarily hydrogen and carbon monoxide; introducingthe non-thermal plasma reactor effluent and the reformate to a selectivereduction catalyst; and reducing the NO_(X) to nitrogen.
 48. The methodof claim 47, wherein the reformate is periodically introduced to theselective catalytic reduction catalyst (20).